Bangladesh police have raided the office of a news website and detained three journalists over a report on rumours the Prime Minister's son had died, an official said today, days after the country blocked dozens of news sites.

Police conducted a five-hour search of the popular news portal banglamail24.com's Dhaka office yesterday evening, hours after the story appeared, and detained the executive editor and two other journalists.

The portal reported rumours published on a Facebook page that Sajeeb Wazed Joy had died in a plane crash, but it made clear that they were false.

"We have picked them up for questioning about the news they have published," said Mufti Mahmud Khan, spokesman for the elite Rapid Action Battalion, which carried out the raid on the office.

"After the questioning ends, we will be able to tell you more about it."

Phones at the banglamail24 office went unanswered today morning and the website had not been updated.

The raid came days after the government sparked accusations of censorship when it shut down 32 online news services, citing "objectionable content".

The government has also banned live television coverage of Islamist extremist attacks in the wake of last month's deadly assault on a cafe in which 22 people were killed, including 18 foreigners.

Prime Minister Shiekh Hasina publicly criticised the coverage of the attack and told private broadcasters to be more responsible.